Heretofore, as exemplified by the patent to Rowlings No. 4,204,785, jigs have been attached to hand power drills so that bores can be drilled through doors parallel to the edges of the door so that a slide bolt can be inserted through the bore to a mortise cavity formed at a suitable place in the edge of the door. The mortise cavity will have a mechanism installed therein which will raise a slide bolt in the door causing it to enter a slide bolt receiving hole in the door jamb thus locking the door. This arrangement is particularly suitable for double door structures whereby one door (controlled by the slide bolt) can be locked, and the adjacent door remains unlocked.
There is not much difficulty in using a drill for boring a hole in any part of a door. But the problem is much more difficult when the bore hole is long and the bore must be exactly parallel to the free swinging edge of the door where the bore hole diameter is not much smaller than the thickness of the door. Consequently, if the bore hole is not precisely parallel to the free swinging edge of the door the bore hole will not reach the mortise cavity but instead will exit the free swinging edge of the door at the wrong place.